The couple - who met starring alongside one another in new action movie X-Men First Class - were spotted taking a romantic stroll through New York's West Village on Sunday morning, but are said to be keeping their relationship "low-key".

An insider explained: "They're really low-key, but they have a great time together just talking music or movies. They really didn't want to be a topic of conversation during the press for X-Men."

Despite the couple's 12-year age gap, Michael, 34, was reportedly attracted to 22-year-old Zoe's "mature" personality and "strong opinions", which is causing her to take the lead in their relationship.

The source added to US Weekly magazine: "Zoe's really mature for her age in that she has very strong opinions and she is very confident in herself. Most people are shocked to learn she's so young; she doesn't really bring it up and age would never stop her from dating anybody.

"For how good looking and smart he is, Michael's pretty shy. She is actually the one taking care of him most the time. She really respects his talent."